Wafer inspection apparatus and method

ABSTRACT

Wafer inspection apparatuses and methods are described. The wafer inspection apparatus includes an optical module, at least one wafer holder for carrying a plurality of wafers, and a plurality of optical sensors. The optical module is configured to emit a plurality of light beams for simultaneously scanning the plurality of wafers carried by the at least one wafer holder. The plurality of optical sensors is configured to receive the light beams reflected by the plurality of wafers.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims the priority benefit of U.S. provisionalapplications Ser. No. 62/880,668, filed on Jul. 31, 2019. The entiretyof the above-mentioned patent application is hereby incorporated byreference herein and made a part of this specification.

BACKGROUND

Fabricating semiconductor devices typically includes processing asubstrate such as a semiconductor wafer using a large number ofsemiconductor fabrication processes to form various features andmultiple levels of the semiconductor devices. The semiconductorfabrication processes may include, but are not limited to, implantationprocesses, deposition processes such as chemical vapor deposition (CVD),plasma-enhanced CVD (PECVD), physical vapor deposition (PVD),lithography and etching processes, grinding and polishing processes, andso on.

Inspection processes are performed at various steps during thefabrication of the semiconductor devices to detect defects on substrates(e.g. wafers) to promote higher yield in the fabricating process andthus higher profits. In the drive for greater efficiencies throughoutthe fabrication process, wafer inspection efficiency is a topic ofinterest.

BRIEF DESCRIPTION OF THE DRAWINGS

Aspects of the present disclosure are best understood from the followingdetailed description when read with the accompanying figures. It isnoted that, in accordance with the standard practice in the industry,various features are not drawn to scale. In fact, the dimensions of thevarious features may be arbitrarily increased or reduced for clarity ofdiscussion.

FIG. 1 is a schematic view of an inspection apparatus in accordance witha first embodiment of the disclosure.

FIG. 2A is a schematic view of an inspection apparatus in accordancewith a second embodiment of the disclosure. FIG. 2B is a schematic viewof the configuration of wafer stages and optical components of theinspection apparatus in accordance with the second embodiment of thedisclosure. FIG. 2C is a perspective view of an optical splittingelement of the inspection apparatus in accordance with the secondembodiment of the disclosure.

FIG. 3 is a schematic view of an inspection apparatus in accordance witha third embodiment of the disclosure.

FIG. 4 is a schematic view of an inspection apparatus in accordance witha fourth embodiment of the disclosure.

FIG. 5 is a schematic view of an inspection apparatus in accordance witha fifth embodiment of the disclosure.

FIG. 6 is a flowchart illustrating an inspection method using theinspection apparatus in accordance with some embodiments of thedisclosure.

FIG. 7 is a schematic cross-sectional view illustrating a wafer carriedby a wafer stage according to some embodiments of the disclosure.

FIG. 8 is a schematic view illustrating an arrayed waveguide grating inaccordance with some embodiments of the disclosure.

DETAILED DESCRIPTION

The following disclosure provides many different embodiments, orexamples, for implementing different features of the provided subjectmatter. Specific examples of components and arrangements are describedbelow for the purposes of conveying the present disclosure in asimplified manner. These are, of course, merely examples and are notintended to be limiting. For example, the formation of a second featureover or on a first feature in the description that follows may includeembodiments in which the second and first features are formed in directcontact, and may also include embodiments in which additional featuresmay be formed between the second and first features, such that thesecond and first features may not be in direct contact. In addition, thesame reference numerals and/or letters may be used to refer to the sameor similar parts in the various examples the present disclosure. Therepeated use of the reference numerals is for the purpose of simplicityand clarity and does not in itself dictate a relationship between thevarious embodiments and/or configurations discussed.

Further, spatially relative terms, such as “beneath”, “below”, “lower”,“on”, “over”, “above”, “upper” and the like, may be used herein tofacilitate the description of one element or feature's relationship toanother element(s) or feature(s) as illustrated in the figures. Thespatially relative terms are intended to encompass differentorientations of the device in use or operation in addition to theorientation depicted in the figures. The apparatus may be otherwiseoriented (rotated 90 degrees or at other orientations) and the spatiallyrelative descriptors used herein may likewise be interpretedaccordingly.

Various embodiments of the disclosure are directed to provide inspectionapparatus (e.g., wafer inspection apparatus) capable of implementingmulti-wafer inspection, so as to improve inspection efficiency.

FIG. 1 is a schematic view of an inspection apparatus 100 in accordancewith at least one embodiment of the disclosure.

Referring to FIG. 1, in some embodiments, the inspection apparatus 100is configured to inspect at least two workpieces W1, W2. The inspectionapparatus 100 may produce images of inspected workpieces W1, W2 fordetermining whether either or both of the workpieces W1, W2 has adefect. The workpieces W1, W2 may be substrates. The substrate mayinclude glass, silicon, ceramic, metal, stainless steel, plastic, resin,a composite material, tape, film, or other suitable materials. In someembodiments, the substrate is a semiconductor wafer.

In some embodiments, the inspection apparatus 100 includes an opticalmodule OM1, a workpiece holder 160 for carrying a plurality ofworkpieces W1, W2, one-way mirrors 151, 152, and optical sensors 171,172.

The optical module OM1 is configured to emit a plurality of light beamsfor simultaneously inspecting the workpieces W1, W2 carried by theworkpiece holder 160. In some embodiments, the optical module OM1includes a light source 110, an optical amplifier 120, an opticaldirectional element 130, and an optical splitting element 140. The lightsource 110 is configured to emit a light L, such as a laser beam.

The optical amplifier 120 is configured to amplify and control theintensity of the light L and thus control the intensities of the lightbeams L1, L2 split from the light L. The light L emitted from the lightsource 110 may be further intensified efficiently by using the opticalamplifier 120, in order to provide desired optical intensity. In someembodiments, the optical amplifier 120 increases the intensity of thelight L to twice or four times or more of its original intensityaccording to product design and requirement. In some embodiments, theoptical amplifier 120 may be a solid-state amplifier, a doped fiberamplifier or a semiconductor optical amplifier, but the disclosure isnot limited thereto. In some embodiments, the optical amplifier 120 is alaser amplifier, such as an RF pumped, fast axial flow, CO₂ laseramplifier. In some embodiments, the optical amplifier 120 is disposedimmediately adjacent to the light source 110, but the disclosure is notlimited thereto. Alternatively or additionally, the optical amplifier(s)may be disposed at other positions to adjust the intensity of the lightbefore the light is directed to the workpieces. For example, the opticalamplifier may be disposed between the optical direction element 130 andthe optical splitting element 140, or disposed between the opticalsplitting element 140 and the workpiece holder 160. However, thedisclosure is not limited thereto.

In some embodiments, the optical module OM1 may optionally include theoptical directional element 130 for controlling the optical path of thelight L. In some embodiments, the optical directional element 130includes a reflector unit. The reflector unit may include a plurality ofreflective mirrors for guiding the light L in an intended direction. Theoptical direction element 130 may include reflective mirrors 131, 132and 133, which may also be referred to as a trombone mirror unit (TMU).Number and configuration of the reflective mirrors included in theoptical direction element 130 shown in the figure is merely forillustration, and the disclosure is not limited thereto. Embodimentsincluding other suitable optical elements which can control the opticalpath of light are also contemplated herein.

The optical splitting element 140 is configured to split the light Linto a plurality of light beams for inspecting multiple workpiecescarried by the workpiece holder 160. In some embodiments, the opticalsplitting element 140 may split the light L into two light beams L1, L2along two opposite vertical directions. The light L may be uniformlysplit into the two light beams, with the intensity of each of the twolight beams being about half the intensity of the light L, but thedisclosure is not limited thereto. In some embodiments, the opticalsplitting element 140 includes a beam splitter 142 and a totalreflection mirror 144. When a light is directed to the optical splittingelement 140, a portion of (e.g. half of) the incident light is reflectedby the beam splitter 142, and another portion of (e.g. half of) of theincident light transmits through the beam splitter 142 and is reflectedby the total reflection mirror 144. The beam splitter 142 may split anunpolarized light into two unpolarized lights, or split a polarizedlight (e.g. p-polarized light or s-polarized light) into two polarizedlights, or split an unpolarized light into two polarized light (e.g.p-polarized light and s-polarized light). In some embodiments, theoptical splitting element 140 is configured to be fixed during waferinspection.

In some embodiments, the optical module OM1 further includes one or morepolarizers configured to polarize the lights to be directed toworkpieces carried by the workpiece holder 160, and the lights mayrespectively be polarized as p-polarized light or s-polarized lightdepending on the type of the defect to be detected. A polarizer 180 maybe disposed along the light path of the light L at a position before thelight L enters the optical splitting element 140 and configured topolarize the light L before being split by the optical splitting element140. The polarizer 180 may be disposed between the optical directionalelement 130 and the optical splitting element 140. In some embodiments,the polarizer 180 is omitted, and one or more polarizers (not shown) areconfigured to polarize the light beam(s) L1, L2 after the light L issplit by the optical splitting element 140. One or more polarizers maybe disposed between the optical splitting element 140 and the workpieceW1 and/or between the optical splitting element 140 and the workpieceW2, such as between the beam splitter 142 and the one-way mirror 151and/or between the total reflection mirror 144 and the one-way mirror152. In some embodiments, the beam splitter 142 is a polarizing beamsplitter for splitting an unpolarized light into two polarized lights.The beam splitter 142 may transmit p-polarized light and reflects-polarized light.

In some embodiments, the workpiece holder 160 includes a plurality ofworkpiece stages 161, 162 for carrying a plurality of workpieces W1, W2.The workpieces W1, W2 may be substrates, such as wafers. Accordingly,the workpiece holder 160 may include substrate holders, such as waferholders, and the workpiece stages 161, 162 may be substrate stages, suchas wafer stages.

In some embodiments, the wafer holder 160 includes a first wafer stage161 for carrying a first wafer W1, a second wafer stage 162 for carryinga second wafer W2, and a connecting element 165 for connecting the firstand second wafer stages 161 and 162. In some embodiments, the firstwafer stage W1 and the second wafer stage W2 are connected to oppositeends of the connecting element 165, and are fixed on the connectingelement 165. Herein, the wafer stages being fixed on the connectingelement means that the relative positional relation between the waferstages and the connecting element are fixed. The connecting element 165may be connected to sidewalls of the wafer stages 161 and 162, but thedisclosure is not limited thereto. In some embodiments, the connectingelement 165 is connected to back surfaces of the wafer stages 161 and162. Herein, the back surface of the wafer stage refers to the surfaceopposite to the front surface 10 (i.e. receiving surface 10) of thewafer stage for receiving a wafer. In some embodiments, the wafer stages161, 162 are symmetric about the connecting element 165, but thedisclosure is not limited thereto. In some embodiments, the wafer stages161, 162 are configured as face to face, such that the front surfaces F1of wafers W1, W2 to be inspected are configured as face to face. In someembodiments, the wafer stages 161, 162 are disposed at opposite sides ofthe optical splitting element 140.

In some embodiments, the wafer holder 160 is operable. For example, thewafer holder 160 is able to rotate about a rotation axis RA. Therotation axis RA may be along the horizontal direction X which passesthrough the center of the connecting element 165. The rotation axis RAis along a direction parallel with the receiving surfaces 10 of thewafer stages 161 and 162 or the front surfaces F1 of the wafers W1, W2carried by the wafer stages. In some embodiments, the wafer holder 160rotates about the rotation axis RA in a clockwise or a counterclockwisedirection by any reasonable degree (e.g. 0 to 360 degrees). That is tosay, the wafer stages 161, 162 of the wafer holder 160 are able torotate about the rotation axis RA, such that the wafers W1, W2 carriedby the wafer stages 161, 162 of the wafer holder 160 rotate as the waferholder 160 rotates. In some embodiments, during wafer inspection, thewafer holder 160 stops rotating and is located at the inspectionposition as shown in FIG. 1. In some embodiments, the wafer stages 161,162 are located at opposite vertical sides of the optical splittingelement 140 and are overlapped with the optical splitting element 140 inthe vertical direction Z during inspection. In some embodiments, thefirst wafer stage 161 is disposed below the optical splitting element140, and the second wafer stage 162 is disposed over the opticalsplitting element 140. The wafer holder 160 is movable along thehorizontal directions, such as the directions X, Y.

In alternative embodiments, the wafer holder 160 is movable in thehorizontal directions, such as the directions X, Y, but is notrotatable. For example, the wafer holder 160 is configured to be fixedat the inspection position as shown in FIG. 1 and is not rotatable.

In the present embodiments, when the wafer holder 160 moves along thehorizontal direction (e.g. direction X or direction Y), the wafers W1,W2 carried by the wafer holder 160 simultaneously move along a samedirection as the wafer holder 160 moves.

In some embodiments, the wafer stages 161, 162 are or include anelectrostatic chuck (E-chuck), respectively. The E-chucks use anelectric force to secure the wafers W1, W2. In other embodiments, thewafer stages 161, 162 respectively include a chuck that uses clamps tosecure the wafers W1, W2. In alternative embodiments, the wafer stages161, 162 respectively include a vacuum chuck that generates vacuumpressure through vacuum ports in the chuck to hold the wafers W1, W2thereon. Combinations of the above chucks may also be used. However, thedisclosure is not limited thereto. The wafers W1, W2 may be carried bythe wafer stages 161, 162 through any appropriate mounting force.

FIG. 7 is a schematic cross-sectional view illustrating a wafer Wcarried by a wafer stage WS including an E-chuck. The wafer stage WS maybe one of the wafer stages 161, 162, and the wafer W may be thecorresponding one of the wafers W1, W2.

Referring to FIG. 7, in some embodiments, the E-chuck of the wafer stageWS includes an electrode EC embedded near the receiving surface 10 forreceiving the wafer W, and the receiving surface 10 is directly over andoverlaps the electrode EC. The electrode EC may be covered by adielectric material such as an oxide or a ceramic, or the like, so as toseparate the electrode EC from the wafer W. In other words, thereceiving surface 10 is a surface of the dielectric material. In someembodiments, the electrode EC is electrically coupled to a power source(not shown). A voltage provided by the power source may be applied tothe electrode EC. In some embodiments, the power source may beconfigured to provide a direct current (DC) or alternating current (AC)power to the electrode EC. In some other embodiments, the power sourceis configured to provide radio frequency (RF) power to the electrode EC.In a chucking mode, the power source is turned on, and a high voltage isprovided by the power source and applied to the electrode EC. Theelectrode EC is then charged to generate an electrostatic force toattract the wafer W, such that the wafer W is secured by the wafer stageWS. In some embodiments, the wafer W is in contact with the receivingsurface 10 of the dielectric material, but the disclosure is not limitedthereto. In alternative embodiments, a supporting element (not shown)may be disposed between the wafer W and the receiving surface 10, suchthat the wafer W is not in direct contact with the receiving surface 10and a gap exists between the wafer W and the receiving surface 10 of thewafer stage WS. The wafer W has a front surface F1 and a back surfaceF2. Throughout the specification, the front surface F1 of the waferrefers to the surface to be inspected, and the back surface F2 of thewafer refers to the surface opposite to the front surface and facing thereceiving surface of the wafer stage. That is, the back surface F2 ofthe wafer W may be in contact with or separate from the receivingsurface 10 of the wafer stage WS. In a de-chucking mode, the powersource is turned off, and the electrostatic force is eliminated, suchthat the wafer W may be removed from the wafer stage WS.

Referring back to FIG. 1, in some embodiments, the optical splittingelement 140 is located between the wafer stage 161 and the wafer stage162. In some embodiments, the distance between the optical splittingelement 140 and the wafer stage 161 and the distance between the opticalsplitting element 140 and the wafer stage 162 are the same or different.

The one-way mirrors 151 and 152 are disposed between the opticalsplitting element 140 and the wafer stages 161 and 162, respectively. Insome embodiments, the one-way mirror is configured to transmit the lightincoming from a first side, and reflect the light incoming from a secondside opposite to the first side.

The optical sensors 171, 172 are configured to receive the light beamsreflected by the wafers W1, W2, and generate the inspection results(e.g. images) of the wafers W1, W2. In some embodiments, the opticalsensors 171, 172 may include time delay and integration (TDI) sensors,but the disclosure is not limited thereto. Other suitable optical imagecapturing components may also be used.

FIG. 6 is a flowchart of an inspection method using the inspectionapparatus described herein. Although the method is illustrated and/ordescribed as a series of acts (processes) or events, it will beappreciated that the method is not limited to the illustrated orderingor acts. Thus, in some embodiments, the acts may be carried out indifferent orders than illustrated, and/or may be carried outconcurrently. Further, in some embodiments, the illustrated acts orevents may be subdivided into multiple acts or events, which may becarried out at separate times or concurrently with other acts orsub-acts. In some embodiments, some illustrated acts or events may beomitted, and other un-illustrated acts or events may be included.

The inspection method may be used to inspect any kind of workpiece, suchas a substrate. In some embodiments, the substrate is a semiconductorwafer, and an illustrative embodiment of a wafer inspection method isdescribed as below with reference to FIG. 1 and FIG. 6.

Referring to FIG. 1 and FIG. 6, in some embodiments, the wafers may beloaded to the inspection apparatus before or after the processing ofwafer(s). For example, after the wafer(s) is/are subjected to depositionprocess(es), such as CVD, PECVD to deposit a dielectric layer or apolymer layer, lithography and etching processes, chemical mechanicalpolishing (CMP) processes and/or any other appropriate semiconductorfabrication processes, the wafers W1, W2 are loaded to the inspectionapparatus to be inspected, so as to determine whether the wafers havedefect. In some embodiments, the wafer holder includes a plurality ofwafer stages, and multiple wafers carried by multiple wafer stages areinspected simultaneously.

In some embodiments, at act 610, a plurality of wafers are loaded to thewafer stages of the wafer holder. For example, the wafer W1 is loaded tothe wafer stage 161 of the wafer holder 160, and the wafer W2 is loadedto the wafer stage 162 of the wafer holder 160. The wafers W1, W2 may becarried by the wafer stages 161, 162 by electrostatic force and/ormechanical force. In some embodiments in which the wafer holder 160 isrotatable, the loading of the each of the wafers W1, W2 is performed ata loading position. The loading position refers to a position where thereceiving surface 10 of the wafer stage 161 or the wafer stage 162 facesupward, such as the position of the wafer stage 161 shown in FIG. 1. Insome embodiments, before the wafers W1, W2 are loaded, the wafer stage162 rotates to the loading position (i.e. the position where the waferstage 161 is located shown in FIG. 1) such that the receiving surface 10of the wafer stage 162 faces upward. The wafer stage 162 is at a lowerposition for loading, and the wafer stage 161 is at an upper positionover the wafer stage 162 (not shown). Thereafter, the wafer W2 is loadedonto the receiving surface 10 of the wafer stage 162 with the frontsurface F 1 of the wafer W2 facing upward. In some embodiments, thewafer W2 is placed on the wafer stage 162 by a mechanical arm (notshown), with the front surface F1 thereof facing up. Thereafter, in someembodiments in which the wafer stage 162 includes an E-chuck asdescribed in FIG. 7, the power source of the E-chuck is turned on, andthe electrode EC is charged to generate an electrostatic force toattract the wafer W2, such that the wafer W2 is secured by the waferstage 162.

After the wafer W2 is held by the wafer stage 162, the mechanical armmoves away. The wafer holder 160 then rotates around the rotation axisRA by 180 degrees along clockwise or counterclockwise direction. Thatis, the wafer holder 160 is flipped upside down, such that the waferstage 161 rotates to the loading position with the receiving surface 10thereof facing upward for loading a wafer, while the wafer W2 carried bythe wafer stage 162 is moved to the upper position as shown in FIG. 1and the front surface F 1 of the wafer W2 faces downward. In someembodiments, the electrostatic force generated by the E-chuck of thewafer stage is strong enough to avoid the wafer W2 detaching from thewafer stage 162 when the wafer stage 162 rotates to the upper position.

Thereafter, the wafer W1 is loaded to the wafer stage 161 by the loadingmethod similar to that of the wafer W2 as described above. The wafer W1is placed on the wafer stage 161 by the mechanical arm (not shown) withthe front surface F1 of the wafer W1 facing up. In the embodiments iswhich the wafer stage 161 includes a E-chuck (FIG. 7), the power sourceof the S-chuck is turned on, and the electrode EC is charged to generatean electrostatic force to attract the wafer W1, such that the wafer W1is secured by the wafer stage 161.

After the wafers W1, W2 are secured by the wafer stages 161, 162, thewafer holder 160 may rotate to the inspection position and stop rotatingfor wafer inspection. An inspection position refers to the position ofthe wafer holder 160 during inspection. In some embodiments, the waferstages 161, 162 are located at opposite vertical sides of the opticalsplitting element 140, as shown in FIG. 1.

In some embodiments in which the wafer holder 160 is not rotatable, thewafer stages 161, 162 are designed and configured to be at theinspection position. The wafers W1, W2 are respectively loaded to thewafer stages 161, 162 at the position shown in FIG. 1. In someembodiments, the first wafer stage 161 is at the lower position and thesecond wafer stage 162 is at the upper position. The receiving surfaces10 of the wafer stages 161, 162 are in a face-to-face configuration. Thereceiving surface 10 of the wafer stage 161 faces upward, while thereceiving surface 10 of the wafer stage 162 faces downward. The wafer W1is placed on the wafer stage 161 by a mechanical arm with the frontsurface F1 of the wafer W1 facing up, and the wafer W1 is then securedby the wafer stage 161 through electrostatic force and/or mechanicalforce, for example. The wafer W2 is moved to the wafer stage 162 at theupper position by a mechanical arm, such that the front surface F1 ofthe second wafer W2 faces downward. In some embodiments, the wafer stage162 includes an E-chuck to attract and secure the wafer W2 byelectrostatic force. In some other embodiments, the wafer stage 162includes both a clamp and an E-chuck. The clamp provides initial forceto hold the wafer W2 by mechanical force, then the E-chuck attracts thewafer W2 by electrostatic force, so as to hold the wafer W2 firmly. Insome embodiments, the electrostatic force is strong enough to preventdetachment of the wafer W2 from the wafer stage 162. After the wafersW1, W2 are held by the wafer stages 161, 162, the mechanical arms moveaway. In some embodiments, one mechanical arm is used to load the wafersW1, W2 to the wafer stages 161, 162 sequentially. In alternativeembodiments, two mechanical arms are used to load the first wafer W1 andthe second wafer W2 simultaneously.

In some embodiments, after the wafers are loaded to the wafer stages, analignment is executed, as shown in the act 620 of FIG. 6. In someembodiments, the inspection method adopts a wafer coordinate system fordetermining and recording the positions of a point (such as a defect) ofthe wafer. The coordinate system includes an x coordinate and a ycoordinate, and a coordinate of the point may be expressed as (x value,y value). In some embodiments, the alignment is executed to determine areference point of the wafer as an origin of the wafer coordinatesystem, and the coordinates of all points on the wafer are determinedwith respect to the origin. In some embodiments, after the wafers W1, W2are secured in place by the wafer stages 161, 162, light beams, such asthe light beams L1, L2 emitted from the optical module OM1, irradiatethe wafers W1, W2, respectively. The points aligned with the light beamsL1, L2 may be selected to be the origin of the wafer coordinate systemof the wafer W1, W2. In some embodiments, an alignment mark is disposedat each origin of the wafers W1, W2. The above alignment method is butone suitable process for determining an origin of wafer coordinatesystem, and any other appropriate alignment method in the field may alsobe used.

At act 630, a plurality of wafers such as the wafers W1 and W2 areinspected simultaneously. In some embodiments, the act 630 includes theact 631(emitting light from a light source), the act 632 (splitting thelight into light beams) and the act 633 (receiving the light beamsreflected by the wafers). More detailed description of each of theseacts 631, 632, 633 follows.

At act 631, a light is emitted from a light source. In some embodiments,a light L, such as a laser beam, is emitted by the light source 110. Insome embodiments, the light L emitted by the light source 110 enters anoptical amplifier 120, and is amplified by the optical amplifier 120.The optical amplifier 120 controls the optical intensity of the light Land increases the optical intensity of the light L to any desiredintensity.

At act 632, the light L is split into a plurality of light beams, andthe plurality of light beams are directed to the wafers W1, W2 formulti-wafer inspection. In some embodiments, after the light L isamplified by the optical amplifier 120, the light L is guided to theoptical splitting element 140 by the optical directional element 130. Insome embodiments, the light L enters the optical directional element130, and is reflected by the reflective mirrors 131, 132, 133 insequence, and then directed toward the optical splitting element 140.

Thereafter, the light L is split by the optical splitting element 140into a first light beam L1 and a second light beam L2 along differentlight paths for inspecting the wafers W1, W2, respectively. In someembodiments, the light L enters the beam splitter 142 and is split bythe beam splitter 142 into a first light beam L1 and a second light beamL2. In some embodiments, a portion (such as, half) of the light L isreflected by the beam splitter 142 as the first light beam L1 directedtoward the wafer W1. Another portion (such as, half) of the light Ltransmits through the beam splitter 142 as the second light beam L2. Thesecond light beam L2 is then reflected by the total reflection mirror144 and is directed toward the wafer W2. In some embodiments, the firstlight beam L1 and the second light beam L2 exiting from the opticalsplitting element 140 exit in opposite directions along the verticaldirection Z. In some embodiments, the first light beam L1 travelsdownward to the wafer W1, and the second light beam L2 travels upward tothe wafer W2.

In some embodiments, the first light beam L1 coming out from the opticalsplitting element 140 passes through the one-way mirror 151 and shineson the front surface F1 of the wafer W1. The second light beam L2 comingout from the optical splitting element 140 passes through the one-waymirror 152 and shines on the front surface F1 of the wafer W2. In someembodiments, the light beams L1, L2 are directed to the wafers W1, W2 ata substantially normal angle of incidence.

With the first light beam L1 and the second light beam L2 shining on thefront surfaces F1 of the wafers W1, W2, the wafer holder 160 moves inthe horizontal directions, such as the directions X, Y. Meanwhile, theoptical splitting element 140 is fixed. As such, the wafers W1 and W2carried by the wafer holder 160 simultaneously move along the samehorizontal directions as the wafer holder 160 moves, such that the wholefront surfaces F1 of the wafers W1 and W2 are scanned by the first lightbeam L1 and the second light beam L2, respectively. In some embodiments,the first light beam L1 and the second light beam L2 shinning on thewafers W1 and W2 may have the same intensities, and the intensity ofeach of the first light beam L1 and the second light beam L2 may be halfof the intensity of the light L after being amplified by the opticalamplifier 120.

In some embodiments, depending on the type of defect to be inspected,the wafer may be scanned by a polarized light or an unpolarized light,that is, the first beam L1 and the second light beam L2 directed to thewafers W1 and W2 may respectively be a polarized (e.g. s-polarized orp-polarized) light or an unpolarized light. In some embodiments in whichthe polarizer 180 is disposed before the optical splitting element 140,the light L emitted by the light source 110 is polarized before thelight L is split by the optical splitting element 140, and the light Lmay be polarized as a p-polarized or s-polarized light. The polarizedlight L is split by the optical splitting element 140 into polarizedlight beams L1 and L2. In such embodiments, the first and second lightbeams L1 and L2 have the same polarization. In some other embodiments,the light may be polarized after being split into the first and secondlight beams. In some embodiments in which the polarizer 180 is omitted,and one or more polarizers are disposed between the optical splittingelement 140 and the one-way mirror 151 and/or between the opticalsplitting element 140 and one-way mirror 152, the light L is firstlysplit into the first light beam L1 and the second light beam L2, andthereafter, the first light beam L 1 and/or the second light beam L2 maybe polarized before transmitting through the one-way mirror 151 and/or152. In such embodiments, at least one of the first and second lightbeams L1 and L2 shining on the wafers W1 and W2 is polarized, and thepolarization of the first and second light beams L1 and L2 may be thesame or different. In some embodiments in which the optical splittingelement 140 is a polarizing optical splitting element, the light L issplit into two polarized light L1 and L2 having different polarizations.In some embodiments, the first light beam L1 is p-polarized light, andthe second light beam L2 is s-polarized light. In some embodiments, thepolarizers are omitted, and unpolarized light L is split by the opticalsplitting element 140 into two unpolarized light beams L1 and L2.

At act 633, the light beams L 1, L2 reflected by the wafers W1, W2 arereceived by the optical sensors 171, 172, so as to generate theinspection results of the wafers W1, W2. In some embodiments, the firstlight beam L1 and the second light beam L2 shone on the wafers W1 and W2are reflected by the front surfaces F1 of the wafers W1 and W2,respectively. The first light beam L1 reflected by the wafer W1 is thenreflected by the one-way mirror 151 and directed to the optical sensor171. The second light beam L2 reflected by the wafer W2 is thenreflected by the one-way mirror 152 and directed toward the opticalsensor 172.

The optical sensor 171 receives the first light beam L1 reflected fromthe wafer W1, and generates an inspection result of the wafer W1. Theoptical sensor 172 receives the second light beam L2 reflected from thewafer W2, and generates an inspection result of the wafer W2.

At act 640, the inspection results of wafers are saved for furtheranalysis. In some embodiments, the inspection results may be transmittedto and stored by a storage medium, such as a computing system. In someembodiments, the inspection results are the images of the front surfacesF1 of the wafers W1 and W2. In some embodiments, neighbor-die comparisonmethod is performed to determine whether the wafer W1, W2 has a defector not. Taking the wafer W1 as an example, the image of the wafer W1captured by the optical sensor 171 includes the images of a plurality ofdies in die regions of the wafer W1. The image of one die (namely,center die) is compared to images of its immediate neighbor dies usingan optical testing method. The method then moves to the next die andcompares the image of the next die against the images of its neighbordie. The above comparison is repeated until all of the dies in the waferW1 have been compared. During the comparison, if any difference (whichmay be a defect) is found, the difference is noted and the die havingthe difference is marked. In some embodiments, the coordinate of thedifference in the wafer coordinate system is recorded. The coordinate ofthe difference refers to the position of the difference with respect tothe origin of the wafer coordinate system determined at act 620.Thereafter, a defect review process is performed. In some embodiments,the wafer W1 is inspected again by a scanning electron microscope (SEM)to get a clearer image of the wafer W1 to double-check the differenceand to determine whether the wafer W1 has a defect. In some embodiments,another appropriate comparison method may be used. In some embodiments,the images of the wafers W1 and W2 are compared with reference images todetermine whether the wafers W1 and W2 have defects. In someembodiments, the reference images may be images of wafers with orwithout defects.

At act 650, the wafers W1 and W2 are unloaded from the wafer stages 161and 162. In some embodiments, the power source of the E-chuck is turnedoff, and the wafer W1, W2 is unloaded from the wafer stage 161/162 bymechanical arm for further processing. If the wafer is determined tohave a defect, appropriate processes may be performed to eliminate thedefect before performing further semiconductor fabrication process.

FIG. 2A is a schematic view of an inspection apparatus 200 according tovarious embodiments of the disclosure. FIG. 2B is a schematic view ofthe configuration of wafer stages and optical components of theinspection apparatus 200 according to various embodiments of thedisclosure. FIG. 2B is a right side view of FIG. 2A, and some componentsare omitted in FIG. 2B for sake of brevity. FIG. 2C is a perspectiveview of an optical splitting element of the inspection apparatus 200according to various embodiments of the disclosure. The configuration ofthe defect inspection apparatus 200 is similar to the defect inspectionapparatus 100 shown in FIG. 1, except that four wafers can besimultaneously inspected by the inspection apparatus 200. Like elementsare designated with the same or similar reference numbers for ease ofunderstanding and the details thereof are not repeated herein.

Referring to FIG. 2A and FIG. 2B, in some embodiments, the inspectionapparatus 200 includes the optical module OM2, the wafer holder 160 forcarrying wafers W1 and W2, the wafer holder 260 for carrying wafers W3and W4, the one-way mirrors 151,152, 251, and 252 (one-way mirrors 251and 252 are not shown in FIG. 2A), the optical sensors 171 and 172 andother two optical sensors not shown in the figures. The optical moduleOM2 may emit four light beams for inspecting the wafers W1 to W4simultaneously. In some embodiments, the optical module OM2 includes thelight source 110, the optical amplifier 120, the optical directionalelement 130, and the optical splitting element 240.

In some embodiments, the wafer holder 260 has a similar structure as thewafer holder 160. In some embodiments, the wafer holder 260 includes awafer stage 261 and a wafer stage 262 connected to each other by aconnecting element 265. The structural relations of the wafer stage 261,the wafer stage 262 and the connecting element 265 are similar to thoseof the wafer support 160, which are not described again here. It isnoted that, the connecting element 161 and 265 of the wafer holders 160and 260 are not shown in FIG. 2B for the sake of brevity. It should beunderstood that, in FIG. 2B, the wafer stages 161 and 162 are connectedto each other by the connecting element 165, and the wafer stages 261and 262 are connected to each other by the connecting element 265.

In some embodiments, similar to the wafer holder 160, the wafer holder260 is also rotatable around the rotation axis RA by any reasonabledegree, and the wafers carried by the wafer holder 260 may rotate aroundthe rotation axis RA as the wafer holder 260 rotates. In alternativeembodiments, the wafer holders 160 and 260 are not rotatable. In someembodiments, the wafer holder 160 is movable in the horizontaldirections X and Y, while the wafer holder 260 is movable in thevertical direction Z and the horizontal direction X, such that thewafers carried by the wafer holders 160 and 260 may move along thecorresponding directions as the wafer holders move. In some embodiments,the wafer holders 160 and 260 are separate from each other and mayseparately move along the same or different directions during the waferinspection. In some embodiments, the inspection position of the waferholders 160 and 260 are as shown in FIG. 2A and FIG. 2B, the waferstages 161 and 162 of the wafer holder 160 are configured at oppositevertical sides of the optical splitting element 240, and the waferstages 261 and 262 of the wafer holder 260 are configured at oppositelateral sides of the optical splitting element 240.

In some embodiments, the optical splitting element 240 of the opticalmodule OM2 may split the light from the light source 110 into four lightbeams L1-L4 for inspecting four wafers W1-W4 carried by the waferholders 160 and 260. In some embodiments, as shown in FIG. 2A and FIG.2C, the optical splitting element 240 includes a first beam splitter242, a second beam splitter 244, a third beam splitter 246 and a totalreflection mirror 248.

In some embodiments, besides the optical amplifier 120, the opticalmodule OM2 further includes a plurality of optical amplifiers (notshown) before and/or after the light being split by a beam splitter, soas to control the intensities of the light beams shone on the wafers. Insome embodiments, as shown in FIG. 2A and FIG. 2B, optical amplifiers281-284 are configured to amplify the light beams L1-L4, respectively.In detail, a first optical amplifier 281 is disposed between the firstbeam splitter 242 of the optical splitting element 240 and the one-waymirror 151; a second optical amplifier 282 is disposed between thesecond beam splitter 244 of the optical splitting element 240 and theone-way mirror 152; a third optical amplifier 283 is disposed betweenthe third beam splitter 246 of the optical splitting element 240 and theone-way mirror 251; and a fourth optical amplifier 284 is disposedbetween the total reflection mirror 248 of the optical splitting element240 and the one-way mirror 252. In some embodiments, the opticalamplifiers are arranged between the first beam splitter 242 and thesecond beam splitter 244, between the second beam splitter 244 and thethird beam splitter 246, and/or between the third beam splitter 246 andthe total reflection mirror 248. In alternative embodiments, with theoptical amplifiers described above, the optical amplifier 120 may beomitted.

When the light is split by the beam splitters 242, 244, and 246, theintensity of the light will drop after being split. With the opticalamplifiers arranged on the optical paths, the light beams L1-L4 can beadjusted and controlled within a suitable range for inspecting thewafers W1 to W4. In some embodiments, the light beams L1 to L4 may becontrolled to have substantially the same intensity to shine on thewafers.

In some embodiments, the optical module OM2 of the inspection apparatus200 is free of any polarizer. In alternative embodiments, the opticalmodule OM2 may include one or more polarizer for polarizing one or moreof the light beams L1-L4, and the one or more polarizer may be disposedbetween the optical splitting element 240 and the one-way mirrors151/152/251/252, or between the optical directional element 130 and theoptical splitting element 240.

The inspection method using the inspection apparatus 200 is describedbelow with reference to FIG. 2A to FIG. 2C and FIG. 6.

At act 610 and act 620, the wafers W1 and W2 are loaded to the waferstages 161 and 162 of the wafer holder 160, the wafers W3 and W4 areloaded to wafer stages 261 and 262 of the wafer holder 260,respectively, and an alignment process is performed to determine originsof the wafer coordinate systems of the wafers. The loading method andalignment method are similar to those described with reference toFIG. 1. In some embodiments in which the wafer holders 160 and 260 arerotatable, each wafer may be loaded to the corresponding wafer stage atthe loading position with the receiving surface of the wafer stagefacing up. In some embodiments, before loading a wafer, one of the waferstages 161,162,261,262 rotates to the loading position for loading oneof the wafers W1-W4, and thereafter, the wafer stage carrying the waferrotates to another position, and another one of the wafer stages rotatesto the loading position for loading another one of the wafers. Herein,the loading position refers to the position where the receiving surfaceof the wafer stage faces up, such as the position where the wafer stage161 is located shown in FIG. 2A. Thereafter, the rotation and waferloading are repeated until the four wafers W1 -W4 are loaded to the fourwafer stages 161, 162, 261, 261, respectively. As described above, thewafers W1 to W4 may be secured by the wafer stages through electrostaticforce and/or mechanical force.

In some embodiments, after the wafers W1-W4 have been loaded to thewafer stages 161,162, 261, 262 in place, the wafer holders 160 and 260rotate to the inspection position for wafer inspection. In someembodiments, the wafer stages of the wafer holder 160 rotate to overlapthe optical splitting element 240 in the vertical direction Z, such thatthe wafers W1 and W2 carried by the wafer stages 161 and 162 are locatedon opposite vertical sides of the optical splitting element 240. Thewafer stages of the wafer holder 260 rotate to overlap the opticalsplitting element 240 in the horizontal direction Y, such that thewafers W3 and W4 carried by the wafer stages 261 and 262 are located onopposite lateral sides of the optical splitting element 240. In someembodiments, the vertical distance between the wafer W1 and the opticalsplitting element 240 is substantially the same as or different from thevertical distance between the wafer W2 and the optical splitting element240, and the lateral distance between the wafer W3 and the opticalsplitting element 240 is substantially the same as or different from thelateral distance between the wafer W4 and the optical splitting element240. Thereafter, the wafer holders 160 and 260 may stop rotating andkeep at the inspection position for wafer inspection.

In some embodiments in which the wafer holders 160 and 260 are notrotatable, the wafer holders 160 and 260 are configured at theinspection position, and the wafers W1 to W4 are respectively loaded tothe wafer stages 161, 162, 261, 262 at the position shown in FIG. 2A andFIG. 2B.

Thereafter, at act 630, multi-wafer inspection is performed. In someembodiments, at act 631, the light L is emitted by the light source 110.The light L may be optionally amplified by the amplifier 120.Thereafter, the light L is directed to the optical splitting element 240through the optical direction element 130.

At act 632, the light is split into a plurality of light beams, and thelight beams are directed to the wafers carried by the wafer holders,respectively. In some embodiments, as shown in FIGS. 2A to 2C, the lightL is split by the optical splitting element 240 into a first light beamL1, a second light beam L2, a third light beam L3 and a fourth lightbeam L4 for inspecting the wafers W1-W4, respectively.

In some embodiments, as shown in FIGS. 2A and 2C, the light L firstenters the first beam splitter 242, and is split by the first beamsplitter 242 into two lights L1 and L2′. A first part of the light L isreflected by the first beam splitter 242 and directed toward the waferW1 as a first light beam L1. A second part of the light L (i.e. thelight L2′) goes through the first beam splitter 242 and enters thesecond beam splitter 244.

The light L2′ is then split by the second beam splitter 244 into twolights L2 and L3′. A first part of the light L2′ is reflected by thesecond beam splitter 244 and directed toward the wafer W2 as a secondlight beam L2. A second part of the light L2′, that is, the light L3′goes through the second beam splitter 244 and enters the third beamsplitter 246.

The light L3′ is then split by the third beam splitter 246 into twolights L3 and L4. A first part of the light L3′ is reflected by thethird beam splitter 246 and directed toward the wafer W3 as a thirdlight beam L3. A second part of the light L3′, that is, the light L4,goes through the third beam splitter 246, and the light L4 is thenreflected by the total reflection mirror 248 and directed toward thefourth wafer W4 as a fourth light beam L4.

In some embodiments, as shown in FIG. 2B, after the light L is splitinto the light beams L1-L4, the light beams L1-L4 may be amplified bythe optical amplifiers 281-284, respectively, so as to have suitableintensities for inspecting the wafers. In some embodiments, after beingamplified, the light beams L1 to L4 have substantially the sameintensity. Thereafter, the light beams L1-L4 pass through the one-waymirrors 151, 152, 251, 252 and shine on the front surfaces F1 of thewafers W1-W4, respectively. Depending on the defect to be detected, thelight beams L1 to L4 may be polarized or unpolarized, respectively. Whena polarized light beam is needed, the light beam may be polarized by apolarizer before passing through the one-way mirror.

Referring to FIG. 2A and FIG. 2B, during the inspection, with the lightbeams L1-L4 shining on the front surfaces F1 of the wafers W1-W4, thewafer holder 160 moves along the horizontal directions X and Y, suchthat the wafer stages 161 and 162 carrying the wafers W1 and W2 movealong the horizontal directions X and Y simultaneously; the wafer holder260 moves along the horizontal and vertical directions X and Z, suchthat the wafer stages 261 and 262 carrying the wafers W3 and W4 movesalong the horizontal and vertical directions X and Z simultaneously,such that the whole front surfaces F1 of the wafers W1-W4 are scanned.In some embodiments, the wafer holders 160 and 260 move simultaneouslyalong the same direction or different directions, such that the wafersW1-W4 are inspected simultaneously.

At act 634, the light beams reflected from the wafers are received byoptical sensors and inspection results of the wafers are generated. Insome embodiments, the first light beam L1 is reflected by the wafer W1,and the first light beam L1 reflected by the wafer W1 is then reflectedby the one-way mirror 151 and received by the optical sensor 171. Thesecond light beam L2 is reflected by the wafer W2, and the second lightbeam L2 reflected by the wafer W2 is then reflected by the one-waymirror 152 and received by the optical sensor 172. The third light beamL3 is reflected by the wafer W3, and the third light beam L3 reflectedby the third wafer W3 is then reflected by the one-way mirror 251 andreceived by an optical sensor (not shown). The fourth light beam L4 isreflected by the wafer W4, and the fourth light beam L4 reflected by thewafer W4 is then reflected by the one-way mirror 252 and received by anoptical sensor (not shown). It is noted that, the optical sensors forreceiving the light beams L3 and L4, and the reflections of the lightbeams L3 and L4 from the wafer W3 and W4 to the one-way mirrors 251, 252and the reflections of the light beams L3 and L4 from the one-waymirrors 251, 252 to the optical sensors are similar to those describedwith respect to the light beams L1 and L2 and the optical sensors171/171, and are not specifically shown in the figures.

After receiving the light beams L1-L4 reflected by the wafers W1-W4, theoptical sensors generate the inspection results of the wafers W1-W4,respectively. At act 640, the inspection results (such as images) of thewafers are saved for further analysis. The defect determination methodof the wafers are similar to those described with reference to FIG. 1,which are not described again here. Thereafter, at act 650, the wafersW1-W4 are unloaded from the wafer stages.

FIG. 3 is a schematic view of an inspection apparatus 300 according tosome embodiments of the disclosure. The configuration of the defectinspection apparatus 300 is similar to the defect inspection apparatus100 shown in FIG. 1, except that multiple layers of wafer holders areincluded in the inspection apparatus 300. Like elements are designatedwith the same or similar reference numbers for ease of understanding andthe details thereof are not repeated herein.

Referring to FIG. 3, in some embodiments, the inspection apparatus 300includes an optical module OM3, a wafer holder set including a pluralityof wafer holders (e.g. wafer holder 160 and 360) for carrying aplurality of wafers, one-way mirrors 151, 152, 351, 352, and opticalsensors 171, 172, 371, 372. In some embodiments, the inspectionapparatus 300 includes at least two wafer holders. The plurality ofwafer holders may be arranged in the vertical direction Z and overlapeach other in the vertical direction Z. In some embodiments, theinspection apparatus 300 includes a wafer holder 160 and a wafer holder360 below the wafer holder 160. The wafer holder 360 includessubstantially the same structure as the wafer holder 160. In someembodiments, the wafer holder 360 includes a wafer stage 361 forcarrying a wafer W3 and a wafer stage 362 for carrying a wafer W4connected to each other by a connecting element 365. Similar to thewafer holder 160, the wafer holder 360 may also be rotatable or notrotatable, and is movable along the horizontal directions, such as thedirections X and Y. Although two wafer holders 160 and 360 are shown inFIG. 3, the disclosure is not limited thereto. More than two waferholders may be included in the inspection apparatus 300, as representedby the ellipsis.

The optical module OM3 may include the light source 110, an opticalamplifier 120, an optical directional splitting unit 330, and aplurality of optical splitting elements 140, 340.

The optical directional splitting unit 330 is configured to split thelight L from the light source 110 into a plurality of lights and directthe plurality of lights toward the plurality of optical splittingelements 140, 340. In some embodiments, the optical direction splittingunit 330 includes reflective mirrors 131, 132, one or more beamsplitters, such as the beam splitter 333, and an optical component 334.The optical component 334 may be a total reflection mirror when thewafer holder 360 is the last wafer holder in a wafer hold set, which ismost distal the light source along the path of the optical directionalsplitting unit 330 (e.g. when the wafer holder 360 is a bottommost waferholder). In some embodiments in which more wafer holders are disposedunder the wafer holder 360, the optical component 334 is a beamsplitter, and a total reflection mirror is disposed corresponding to thebottommost wafer holder.

The optical splitting elements 140, 340 are disposed between the waferstages of the corresponding wafer holder 160, 260 and configured tosplit the light from the optical directional splitting unit 330 into aplurality of light beams for inspecting the corresponding wafers. Theconfiguration of each optical splitting element and corresponding waferholder is similar to that of the optical splitting element 140 and thewafer holder 160 as described with reference to FIG. 1.

The inspection method using the inspection apparatus 300 is similar tothat of the inspection apparatus 100. At act 610, the wafers W1-W4 areloaded to the wafer stages 161, 162, 361, 362 of the wafer holders 160,360. In some embodiments, the wafers W1-W4 are carried by the waferstages 161, 162, 361, 362 by electrostatic force and/or mechanicalforce, respectively. At act 620, an alignment is executed to determineorigins of the wafer coordinate system of the wafers W1-W4. Thereafter,at act, multi-wafer inspection is performed.

In some embodiments, at act 631, the light L is emitted by the lightsource 110. The light L may be amplified by the optical amplifier 120before entering the optical directional splitting unit 330. At act 632,the light L is split into a plurality of light beams L1 to L4 directedtoward wafers W1 to W4. In some embodiments, the light L enters theoptical directional splitting unit 330, the light L is reflected by thereflectors 131 and 132 in sequence and then split by the beam splitter333 into two portions L′ and L″. The first portion L′ of the light L isreflected by the beam splitter 333 and directed toward the opticalsplitting element 140. The second portion L″ of the light L transmitsthrough the beam splitter 333 and may be partially or completelyreflected by the optical component 334 and directed toward the opticalsplitting element 340. In some embodiments in which the wafer holder 360is the bottommost wafer holder and the optical component 334 is a totalreflection mirror, the second portion L″ of the light L is substantiallycompletely reflected by the total reflection mirror 334 and directedtoward the optical splitting element 340. In some embodiments in whichother wafer holders are disposed below the wafer holder 360 and thecomponent 334 is a beam splitter, the second portion L″ of the light Lis further split by the beam splitter 334 into two part. In someembodiments, half of the second portion L″ of the light L is reflectedby the beam splitter 334 and directed toward the optical beam splittingelement 340, and the other half of the second portion L″ of the light Ltransmits through the beam splitter 334 for the wafers carried by thewafer holders in next layers. In some embodiments, after the light L issplit into two portions L′ and L″ and before the first portion L′ andthe second portion L″ of the light L enter the optical splittingelements 140 and 340, the first portion L′ and second portion L″ of thelight L are amplified by optical amplifiers (not shown) which may bedisposed between the optical directional splitting element 330 and theoptical splitting elements 140, 340, so as to adjust the intensities ofthe light beams L1-L4 directed to the wafers.

The first portion L′ of the light L is then split by the opticalsplitting element 140 into a first light beam L1 and a second light beamL2 for inspecting the wafers W1 and W2 carried by the wafer holder 160.The second portion L″ of the light L is then split by the opticalsplitting element 340 into a third light beam L3 and a fourth light beamL4 for inspecting the wafers W3 and W4 carried by the wafer holder 360.In some embodiments, the adjusting of the intensities of the light beamsL1-L4 may be performed after the first and second portions L′ and L″being split by the optical splitting elements 140, 340. In someembodiments, the light beams L1-L4 may be amplified to desiredintensities before going through the one-way mirrors by the amplifiers(not shown) disposed between the optical splitting element 140, 340 andthe corresponding one-way mirrors 151, 152, 351, 352. The light beamsL1-L4 may be unpolarized or polarized, respectively. In someembodiments, at least one of the light beams L1-L4 is polarized by thepolarizer(s) (not shown) disposed between the optical splitting elementand the corresponding one-way mirror.

Thereafter, the light beams L1-L4 respectively transmit through acorresponding one-way mirror 151, 152, 351, 352 and shine on the wafersW1-W4, respectively.

During the wafer inspection, with the light beams L1-L4 shining on thewafers W1-W4, the wafer holders 160 and 360 may move along thehorizontal direction X/Y simultaneously, such that the wafers W1-W4carried by the wafer stages of the wafer holders 160 and 360 move alongthe horizontal directions X/Y simultaneously, and the whole frontsurfaces F1 of the wafers W1-W4 may be scanned by the light beams L1-L4,respectively.

At act 634, the light beams L1-L4 are reflected by the wafers W1-W4, andthe light beams reflected by the wafers W1-W4 are then reflected by theone-way mirrors 151, 152, 351, 352 and received by the optical sensors171, 172, 371, 372, respectively. Thereafter, upon receiving the lightbeams L1-L4 reflected by the wafers W1-W4, the optical sensors 171, 172,371, 372 generate the inspection result of the wafers W1-W4, such as theimages of the wafers W1-W4. At act, the inspection result is saved. Atact 650, the wafers W1-W4 are unloaded from the wafer holders 160 and360.

FIG. 4 is a schematic view of an inspection apparatus 400 according to afourth embodiment. The configuration of the inspection apparatus 400 issimilar to the inspection apparatus 100 shown in FIG. 1, except that theoptical directional element is an optical fiber 480 instead of areflective mirror unit. The optical fiber 480 is configured to guide thelight L to the optical splitting element 140. In alternativeembodiments, the optical directional element may include a combinationof reflective mirrors and optical fiber.

In some embodiments, after being amplified by the optical amplifier 120,the light L emitted by the optical source 110 is guided to the opticalsplitting element 140 by the optical fiber 480. The optical fiber 480 ismore flexible in transmitting the light L. Also, by using the opticalfiber 480, the size of the optical directional element may be reduced.The other structures of the inspection apparatus 400 and the inspectionmethod using the inspection apparatus 400 are similar to those describedwith reference to FIG. 1, which are not described again here.

In the foregoing embodiments, the light source 110 is disposed over thewafer holder(s), and the optical directional element is needed to adjustthe light path of the light emitted by the light source 110. However,the disclosure is not limited thereto.

FIG. 5 is a schematic view of an inspection apparatus 500 according toat least one embodiment of the disclosure. The configuration of theinspection apparatus is similar to the defect inspection apparatus shownin FIG. 1, except that the light source 110 is disposed aside the waferholder 160, and the optical splitting element 140 is replaced by anintegrated optical element 520. The integrated optical element 520 isconfigured to split the light from the light source 110 into a pluralityof light beams for inspecting multiple wafers.

In some embodiments, the light source 110 is disposed laterally asidethe integrated optical element 520, and the light L emit from the lightsource 110 is directed toward the integrated optical element 520directly. As such, the directional element for guiding the light L maybe omitted. When the light L enters the integrated optical element 520,the light L is split by the integrated optical element 520 into aplurality of light beams for inspecting the wafers carried by the waferholder 160, respectively.

In some embodiments, the integrated optical element 520 is or includesan optical coupler, arrayed waveguide grating (AWG), combinationsthereof or the like. In some embodiments, the integrated optical element520 includes a plurality of optical components which are combined tofulfill some complex functions. Such optical components, for example,may be optical filters, modulators, amplifiers, splitters or the like.These optical components, for example, can be fabricated on the surfaceof some crystalline material (such as silicon, silica, or LiNbO₃) andconnected with waveguides.

In some embodiments, the integrated optical element 520 includes anarrayed waveguide grating AG. A structure of arrayed waveguide gratingAG in accordance with at least one embodiment is illustrated in FIG. 8.In some embodiments, the arrayed waveguide grating AG includes an inputoptical fiber F, free space propagation regions S1 and S2, a waveguidearray including a plurality of channel waveguides W₁, W₂, W₃ . . .W_(n), and a plurality of output optical fibers F₁, F₂ . . . F_(n). Theinput optical fiber F is configured to input an incident light. The freespace propagation region S1 is coupled to an end of the optical fiber Fand may include an input cavity, coupler part or slab waveguide. Thechannel waveguides W₁, W₂, W₃ . . . W_(n) are connected to an end of thefree space propagation region S1. The channel waveguides have differentlengths and are arranged side by side. The free space propagation regionS2 is connected to ends of the channel waveguides W₁, W₂, W₃ . . . W_(n)and may include an output cavity, coupler part, or slab waveguide. Theoutput optical fibers F₁, F₂ . . . F_(n) are connected to an end of thefree space propagation region S2 and configured to output a plurality oflights split from the incident light. In some embodiments, an incidentlight such as a light L is fed using the optical fiber F into the freespace propagation region S1. The light L may be a wavelength multiplexedlight having various wavelengths. The light L passes through the freepropagation region S1 and enters the channel waveguides W₁, W₂, W₃ . . .W_(n). The phase delay proportional to wavelength is introduced to lightsignals passed from different channel waveguides of different lengths.These phase delayed signals are made to pass from the free propagationregion S2. Light signals after passing through different lengths ofchannel waveguides interfere with one another and are refocused at theoutput optical fibers F₁, F₂ . . . F_(n). As a result, each of theoutput optical fiber F₁, F₂ . . . F_(n) is fed with one uniquewavelength of light having maximum amplitude. In some embodiments, aplurality of lights L₁, L₂ . . . L_(n) is output from the optical fibersF₁, F₂ . . . F_(n). In other words, the incident light having at leasttwo wavelengths is split by the arrayed waveguide grating AG into atleast two lights, and each of the at least two lights has a singlewavelength. It is noted that, the number of the channel waveguides, thenumber of the output optical fibers and the number of lights output fromthe optical fibers are not limited in the disclosure.

Referring back to FIG. 5, the integrated optical element 520 may splitthe light L from the light source 110 into at least two light beams,such as the light beams L1 and L2, for inspecting the wafers W1 and W2.The integrated optical element 520 may further amplify the light L, soas to control the intensities of the light beams directed to the waferscarried by the wafer holder 160. The other structures of the inspectionapparatus 500 and the inspection method using the inspection apparatus500 are similar to those described with reference to FIG. 1, which arenot described again here.

In the embodiments of the disclosure, the inspection apparatus includesone or more wafer holders including a plurality of wafer stages forcarrying a plurality of wafers, and the optical module of the inspectionapparatus is configured to emit a plurality of light beams forinspecting the plurality of wafers simultaneously, so as to implementmulti-wafer inspection. As such, the wafer inspection efficiency isimproved, and the yield is thus improved.

In accordance with some embodiments of the disclosure, a waferinspection apparatus includes a light source, a first optical splittingelement, a first wafer holder, a first optical sensor and a secondoptical sensor. The light source is configured to emit a light. Thefirst optical splitting element is configured to split the light fromthe light source into a first light beam and a second light beam. Thefirst wafer holder includes a first wafer stage for carrying a firstwafer and a second wafer stage for carrying a second wafer. The firstwafer is configured to reflect the first light beam, and the secondwafer is configured to reflect the second light beam. The first opticalsensor is configured to receive the first light beam reflected by thefirst wafer carried by the first wafer stage. The second optical sensoris configured to receive the second light beam reflected by the secondwafer carried by the second wafer stage.

In accordance with some embodiments of the disclosure, a waferinspection apparatus includes an optical module, at least one waferholder for carrying a plurality of wafers and a plurality of opticalsensors. The optical module is configured to emit a plurality of lightbeams for simultaneously scanning the plurality of wafers carried by theat least one wafer holder. The plurality of optical sensors isconfigured to receive the light beams reflected by the plurality ofwafers.

In accordance with some embodiments of the disclosure, a waferinspection method includes: loading a plurality of wafers to at leastone wafer holder; and inspecting the plurality of wafers simultaneously,comprising: emitting a plurality of light beams from an optical module,and the plurality of light beams are directed toward the plurality ofwafers; and receiving the plurality of light beams reflected by thewafers through a plurality of optical sensors.

The foregoing outlines features of several embodiments so that thoseskilled in the art may better understand the aspects of the presentdisclosure. Those skilled in the art should appreciate that they mayreadily use the present disclosure as a basis for designing or modifyingother processes and structures for carrying out the same purposes and/orachieving the same advantages of the embodiments introduced herein.Those skilled in the art should also realize that such equivalentconstructions do not depart from the spirit and scope of the presentdisclosure, and that they may make various changes, substitutions, andalterations herein without departing from the spirit and scope of thepresent disclosure.

What is claimed is:
 1. A wafer inspection apparatus, comprising: a lightsource, configured to emit a light; a first optical splitting element,configured to split the light from the light source into a first lightbeam and a second light beam; a first wafer holder, comprising a firstwafer stage for carrying a first wafer and a second wafer stage forcarrying a second wafer, wherein the first wafer is configured toreflect the first light beam, and the second wafer is configured toreflect the second light beam; a first optical sensor, configured toreceive the first light beam reflected by the first wafer carried by thefirst wafer stage; and a second optical sensor, configured to receivethe second light beam reflected by the second wafer carried by thesecond wafer stage.
 2. The wafer inspection apparatus of claim 1,wherein the first wafer stage comprises a first electrostatic chuck andthe second wafer stage comprises a second electrostatic chuck, and thefirst wafer and the second wafer are carried by the first electrostaticchunk and the second electrostatic chuck through electrostatic forces,respectively.
 3. The wafer inspection apparatus of claim 1, wherein thefirst wafer holder further comprises a connecting element, and the firstwafer stage and the second wafer stage are connected to each otherthrough the connecting element.
 4. The wafer inspection apparatus ofclaim 1, wherein the first wafer holder is rotatable about a rotationaxis along a direction parallel with receiving surfaces of the firstwafer stage and second wafer stage.
 5. The wafer inspection apparatus ofclaim 1, further comprising an optical directional element, wherein theoptical directional element is configured to guide the light emittedfrom the light source to the first optical splitting element.
 6. Thewafer inspection apparatus of claim 5, wherein the optical directionalelement comprises at least one selected from a group of a reflector unitand an optical fiber.
 7. The wafer inspection apparatus of claim 1,further comprising an optical amplifier configured to controlintensities of the first light beam and the second light beam.
 8. Thewafer inspection apparatus of claim 1, further comprising a second waferholder, wherein the second wafer holder comprises a third wafer stagefor carrying a third wafer and a fourth wafer stage for carrying afourth wafer, and the first optical splitting element is furtherconfigured to split the light into a third light beam directed to thethird wafer and a fourth light beam directed to the fourth wafer.
 9. Thewafer inspection apparatus of claim 1, further comprising: an opticaldirectional splitting unit configured to split the light emitted fromthe light source into a first portion and a second portion and directthe first portion to the first optical splitting element and direct thesecond portion to a second optical splitting element, wherein the firstportion is split by the first optical splitting element into the firstlight beam and the second light beam, and the second portion is split bythe second optical splitting element into a third light beam and afourth light beam; and a second wafer holder, comprising a third waferstage for carrying a third wafer and a fourth wafer stage for carrying afourth wafer, wherein the third wafer is configured to reflect the thirdlight beam, and the fourth wafer is configured to reflect the fourthlight beam; a third optical sensor, configured to receive the thirdlight beam reflected by the third wafer; and a fourth optical sensor,configured to receive the fourth light beam reflected by the fourthwafer.
 10. A wafer inspection apparatus, comprising: an optical module;at least one wafer holder for carrying a plurality of wafers, whereinthe optical module is configured to emit a plurality of light beams forsimultaneously scanning the plurality of wafers carried by the at leastone wafer holder; and a plurality of optical sensors, configured toreceive the light beams reflected by the plurality of wafers.
 11. Thewafer inspection apparatus of claim 10, wherein each of the at least onewafer holder comprises two wafer stages connected to each other by aconnecting element.
 12. The wafer inspection apparatus of claim 11,wherein the two wafer stages are configured to be simultaneouslymovable.
 13. The wafer inspection apparatus of claim 11, whereinreceiving surfaces of the two wafer stages for receiving wafers are faceto face.
 14. The wafer inspection apparatus of claim 10, wherein theoptical module comprises: a light source, configured to emit a light; anoptical splitting element, configured to split the light into theplurality of light beams directed toward the wafers carried by the atleast one wafer holder; and at least one amplifier, configured tocontrol intensities of the plurality of light beams.
 15. The waferinspection apparatus of claim 14, wherein the optical module furthercomprises an optical directional element, configured to guide the lightemitted from the light source to the optical splitting element.
 16. Awafer inspection method, comprising: loading a plurality of wafers to atleast one wafer holder; and inspecting the plurality of waferssimultaneously, comprising: emitting a plurality of light beams from anoptical module and the plurality of light beams are directed toward theplurality of wafers; and receiving the plurality of light beamsreflected by the wafers through a plurality of optical sensors.
 17. Themethod of claim 16, wherein loading the plurality of wafers to the atleast one wafer holder comprises: loading a first wafer to a first waferstage of a first wafer holder of the at least one wafer holder; rotatingthe first wafer holder, such that the first wafer holder is flippedupside down; and loading a second wafer to a second wafer stage of thefirst wafer holder.
 18. The method of claim 16, wherein emitting theplurality of light beams from the optical module comprises: emitting alight by a light source; splitting the light into the plurality of lightbeams by at least one optical splitting element; and at least one ofamplifying the light before splitting the light or amplifying theplurality of light beams after splitting the light.
 19. The method ofclaim 16, wherein during inspecting the plurality of wafers, with theplurality of light beams shining on the plurality of wafers, theplurality of wafers move simultaneously as the at least one wafer holdermoves.
 20. The method of claim 16, further comprising polarizing atleast one of the plurality of light beams before being directed toward acorresponding wafer of the plurality of wafers.